1. Field of the Invention
The subject matter disclosed generally relates to the field of semiconductor lasers.
2. Background Information
Semiconductor lasers are used in a variety of system applications. For example, semiconductor lasers are used as a light source in fiber optic communication systems. It is generally desirable to provide a semiconductor laser that has a high power output. High power output reduces the number of repeaters and amplifiers required for the optical system.
FIG. 1 shows a laser diode array 1 that contains a plurality of laser stripes 2 each separated by an unpumped region 3. Each laser stripe 2 emits a laser beam. Collectively, the laser stripes 2 increase the power output of the device 1.
The laser stripes 2 are formed in relative close proximity to each other. Consequently, there is a coupling between stripes 2 due to the electromagnetic fields emitted by the laser beams formed therein. This coupling creates various operating modes.
As shown in FIG. 2 the stripes may be coupled in a coherent xe2x80x9csupermodexe2x80x9d where adjacent stripes operate in-phase. The in-phase supermode creates a high power, high quality diffraction limited output beam.
Unfortunately, most laser diode arrays operate in an anti-phase supermode where adjacent stripes are 180 degrees out of phase from each other. The anti-phase supermode is shown in FIG. 3. In the anti-phase supermode, the intensity profile more closely matches the amplification gain profile of the array, where both gain and light intensity are at a minimum in the unpumped regions that separate the stripes. This matching of intensity and gain tends to induce the array to operate in the anti-phase supermode.
The resultant output beam of a laser diode array operating in the anti-phase supermode has a double peak rabbit ear shape with minimums at 0 degrees. Such a waveform is difficult to focus and is essentially useless for applications that require a high quality, diffraction limited beam.
A laser diode array that includes two or more laser stripes. The laser diode array also includes a phase shifter appended to every second laser stripe.